Analysis of HIV-positive people admitted to a tertiary-care hospital over a 3-year period found a high rate of prescribing errors, most of which were judged potentially harmful [1]. Prescription review by an HIV-specialized pharmacist could have saved the hospital an estimated $24,000 to $124,000 per year for errors caught and corrected during the hospital stay, depending on whether the impact is figured for inpatients or postdischarge patients.

Partly because antiretrovirals interact with so many other drugs and with each other, HIV-positive people are at high risk of drug-drug interactions, especially when being treated for acute conditions in the hospital [2]. Antiretrovirals often require different dosing for people with certain comorbidities or taking potentially interacting drugs.

To evaluate the impact of hospital prescribing errors, researchers at Midwestern University Chicago College of Pharmacy and Northwestern Memorial Hospital in Chicago retrospectively reviewed medication errors in antiretroviral-treated people admitted to Northwestern, a tertiary care hospital, between May 1, 2006 and April 30, 2009.

Two HIV-specialist pharmacists and one physician graded prescription severity for the potential to cause harm in the hospital or after discharge, using the National Coordinating Council for Medication Error Reporting and Prevention (NCC MERP) Index for Categorizing Medication Errors. The investigators based healthcare cost calculations on published estimates of cost avoidance for each category of prescribing error. Category G medication errors are those that could cause major adverse events with cost-avoidance valued at $2200 per error. Category D, E, and F medication errors are those that could cause minor adverse events with cost-avoidance valued at $220 per error. Category A, B, and C medication errors are minor mistakes assigned no cost avoidance value.

The researchers identified 551 prescribing errors in 248 patients during 381 hospital admissions. A large minority of patients with medication errors (41%) had a viral load above 200 copies, and almost half (46%) had a CD4 count below 200. Hospital stays in these people lasted a median of 4.8 days. The investigators calculated an error rate of 11.59 per 100 patient-days. Of the 551 identified errors, 383 (69.5%) occurred within 24 hours of admission. Median time taken to correct an error was 23 hours.

Dosing errors accounted for almost one third of these mistakes, followed by drug-administration errors and drug-interaction errors. Numbers and percents of identified errors follow:

Ranking medication errors for potential to cause harm to inpatients, the investigators rated only 1 error as category G, the worst type of error (0.2%), 3 as F (0.5%), and 2 as E (0.4%). There were 316 category D errors (57%), 218 category C errors (40%), and 11 category A errors (4%). Estimated cost savings based on harm aversion by correcting these errors was $24,273 per year.

Rating medication errors for potential to cause postdischarge harm, the researchers ranked 132 (24%) as category G, 50 (9%) as category F, 186 (34%) as category E, 136 (25%) as category D,
36 (7%) as category C, and 11 (2%) as category A. Based on harm aversion to patients after discharge, correcting these errors would save an estimated $124,000 per year. The greater postdischarge harm ranking and cost savings underline the heightened danger of failing to spot and correct medication errors during the hospital stay.

These investigators concluded that "in hospitalized patients on antiretroviral therapy, medication review by a pharmacist with expertise in HIV therapeutics could be a cost effective approach to reducing healthcare costs and harm associated with medication errors." In this study physicians accepted 93% of prescribing recommendations made by an HIV-specialized pharmacist.

Another recent study of prescribing errors in HIV-positive people admitted to a tertiary-care hospital in Florida also found that most errors happened during the first day after admission [2]. Most errors involved missed doses, underdosing, overdosing, therapy omission, and drug-drug interactions. These researchers blamed "provider lack of knowledge" as the primary cause.